X-ray color electrophotography

ABSTRACT

An electrostatic latent image formed on a photoconductive layer by means of X-ray electrophotography is divided into at least two regions by the degree of electrostatic potential, said regions being represented by different colors after being developed by depositing a different color developer powder on each of said regions.

United States Patent [191 Hukase et al.

X-RAY COLOR ELECTROPHOTOGRAPHY Assignee: Konishiroku Photo Industry Co.,

Ltd., Tokyo, Japan Filed: Feb. 16, 1973 Appl. No.: 333,151

Related US. Application Data Continuation-impart of Ser. No. 130,820,April 2, i971, abandoned.

Foreign Application Priority Data Dec. 10, 1974 [56] References CitedUNITED STATES PATENTS 2,817,598 12/1957 Hayford ll7/l7.5 2,859,3521l/l958 Sugarman, Jr. 3,057,720 10/1962 Hayford et al. 96/l.2

Primary Examiner-James W. Lawrence Assistant ExaminerB. C. AndersonAttorney, Agent, or Firm--Bierman & Bierman [5 7 ABSTRACT Anelectrostatic latent image formed on a photoconductive layer by means ofX-ray electrophotography is Apr. 7, 1970 Japan 45-29052 divided into atleast two regions by the degree of electrostatic potential, said regionsbeing represented by US. Cl. 250/315 different colors after beingdeveloped by depositing a Int. Cl. G01n 23/04 different color developerpowder on each of said re- Field of Search 96/12; 117/175; 250/315,gions.

7 Claims, 8 Drawing Figures 9 e e e f 9 e 9 9 e 9 e 99 l 9699 e999] /-\1L l, 2 I L.

PAIENIEU mi 1 01914 SHEEI 2 OF 3 Fig. 6

Fig.7

Skin

7 Bone Portions Ponions' INVENTORS ATTORNEY anese Application 29052/1970filed Apr. 7, 1970.

The present invention relates to an X-ray photography in which the imagereading capability can be ex tremely enhanced by coloring an X-rayelectrophotograph with two or more colors.

According to the X-ray electrophotography in the prior art, aphoto-sensitive plate prepared by depositing amorphous selenium onto analuminum base plate through evaporation within a vacuuum was charged bycorona discharge in a dark space, shielded from a visible light, loadedwith a subject to be photographed thereon, and then irradiated withX-rays. The X-rays passed through the subject irradiate the seleniumsurface with doses at the respective portions which are reduced as theabsorption at the corrresponding subject portions increases. Since thesurface potential of the selenium is decayed depending upon the amountof doses of the X-rays at the respective portions, an elec: trostaticlatent image of the internal structure of the subject may be formed onthe selenium surface.

At this stage of processing, if developer powders bearing an electriccharge of opposite sign to that of the electrostatic latent image aredispersed on the selenium layer, then the developer powders areattracted to said selenium surface at a density corresponding to themagnitude of the surface potential at the respective portions, wherebythe latent image can be visualized.

After this visualized image has been electrostatically transferred to atransfer sheet, if it is fixed by a means ofa heat or a solvent vapor, apermanently preservable X-ray image can be obtained.

Heretofore, the developer powders were monochromatic powders of theorder of to 1. in size and colored black, blue or white, andconsequently, the reading of the image has been done on the basis of thedifference in density at the various portions.

In the X-ray electrophotography, the contrast of the finished image isfar weaker than that of a silver salt emulsion film. However, on theother hand, due to the edge effect which is inherent to theele'ctrophotography, the edges of the subject were developed distinctly,so that an easily readable image was obtained. In other words, uponreading the image, mainly the contour of the subject has been watchedrather than reading the image of the subject on the basis of thedifference in density.

As described, although it is possible to identify the contour of thesubject by means of the developer of only one color, the presentinvention has made an improvement in that said contour is furtheremphasized with the difference in color so as to be identified morereadily.

More particularly, the present invention has enhanced the image readingcapability by dividing the image into a plurality of sections dependingupon the difference in the surface potential caused by the difference inthe dose of absorbed X-rays, one section being deposited with developerpowders of two or more colors while the other section being depositedwith those of only one color, and by making the internal structurewithin the subject clearly distinguishable on the basis of thedifference in color caused by the color mixing principle.

These and other features and advantages of the present invention willbecome apparent upon a perusal of the following specification taken inconjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic view illustrating the step of charging the surfaceof the photo-sensitive plate with a corona discharge,

FIG. 2 is a schematic view illustrating the step of irradiating thesubject placed on the cassette containing the photosensitive plateaccording to the present invention,

FIGS. 3 and 4 are schematic views illustrating the successive steps ofdeveloping the latent electrostatic image on the photosensitive plateaccording to the present invention,

FIG. 5 is a schematic view illustrating the step of electrostaticallytransferring the developed visible image onto a separate transfer sheet.

FIG. 6 is a schematic view illustrating the step of fixing thetransferred visible image by thermal means, and

FIG. 7 is a diagram showing a potential distribution formed on theselenium surface after the X-ray irradiation,

FIG. 8 is a schematic view illustrating the step of negatively chargingthe aluminum plate for selectively depositing the developing powder.

Referring now to the accompanying drawings, reference numeral (1)designates a selenium layer deposited onto a thin aluminum plate (2) byevaporation. Reference numeral (2a) designates a cassette cover platefor enclosing the charged photo-sensitive plate (1), (2). Referencenumeral (3) designates an X-ray tube, numeral (4) designates a subjectto be photographed, numeral (5) designates an opposite electrode to beopposed to the selenium layer (1) and is connected with the aluminumplate (2) through a power supply (6) upon developing, numeral (7)designates a'developer device according to the powder cloud method,numerals (8) and (8') designate developer powders, numeral (9)designates a transfer sheet for transferring an image (10) thereto,numeral (11) designates a heat source for fixing the image (10), andnumeral (12) designates a corona discharge device for charging theselenium layer (1).

Now examples of the X-ray color electrophotography according to thepresent invention will be described hereinafter.

EXAMPLE 1 On the surface of an aluminum plate (2) of 1.4 mm inthickness, is deposited a selenium layer (1) of 160p. in thickness byevaporation. This selenium layer (1) is charged in a dark space with acorona discharge as shown in FIG. 1 so that the surface potential mayattain +lOOOV. After the charged photo-sensitive plate (1), 2) has beenenclosed by the cassette cover plate (2a), a hand articulation portion(4) is placed on said cassette cover plate (2a) as shown in FIG. 2, andirradiated with X-rays of KV peak in tube voltage and IOOmA in tubecurrent for 0.14 seconds at a distance of Im from the X-ray tube (3).Then the surface potential of the selenium layer 1) is reduced to 740Vat the portions corresponding to the bones and to about 400V at otherportions corresponding to the vessels, skins, etc. Diagrammaticallyrepresenting the potential distri- 3 bution of such an electrostaticlatent image, it shows a potential distribution as illustrated in FIG.7. In other words, between the portions for the bones and the remainingportions, there exists a potential difference of about 340V.

Here, as a method for developing this'electrostatic latent image tovisualize the same, the powder cloud method of blowing type is employed.In the first step of development, the opposite electrode (5) is disposedapart from the selenium layer (1) by l cm as shown in FIG. 3, a biasvoltage of +600V being applied thereto, and the latent image isdeveloped by means of negatively charged blue developer powders (8).Then, the blue developer powders (8) are hardly attracted by theselenium surface portions where the surface potential is lower than600V, while they are attracted only by the portions at a potentialhigher than 600V such as, for example, the portions corresponding to thebones.

Nextly, in a developer device without the opposite electrode (5) (SeeFIG. 4), the latent image is developed by means of negatively chargedred developer powders (8'). Then said red developer powders areattracted by every portion of the latent image having a positivepotential. Subsequently, this visible image (10) is transferred onto atransfer sheet (9) by any known process as illustrated in FIG. 5, andthen the developer powders (8) and (8) are respectively heated and thusfixed by means of the heat source (11). Therefore, the portions Icorresponding to the bones are doubly developed by both the bluedeveloper powders and the red developer powders, resulting in violetimages, while other portions such as corresponding to the vessels,skins, etc. are developed only by the red developer powders.Consequently, identification based on colors is enabled,

and this results in remarkable enhancement of the image readingcapability in comparison to the identification based on only thedifference in density in the prior art.

EXAMPLE 2 On the surface of an aluminum plate (2) of 1.4 mm inthickness, is deposited a selenium layer (1) of 280g. in thicknessby'evaporation in a vacuum. This selenium layer (1) is charged in a darkspace so that the surface potential may attain +2,50OV. Then, a lowerleg injected with 76percent Urograffm as a shadow making agent into thevessel is placed on the cassette cover plate (2a), and irradiated withX-rays of 80 KV peak in tube voltage and 300 mA in tube current for 0.1seconds at a distance of l m from the X-ray tube (3). Then, the surfacepotential at the selenium layer portion corresponding to the vesselportions containing Urograffin which most hardly passes the X-rays,becomes 1,680V, the portions corresponding to the bones take a potentialof l,370V, and other portions corresponding to the skins take apotential of 1,050V. In case that the electrostatic latent image havingsuch a potential distribution is developed by making use of the oppositeelectrrode (5) similarly to the Example 1, at first a voltage of +1500Vis applied to the opposite electrode and the latent image is developedby means of black developer powders. Then the developer powders areattracted only by the portions at a potential higher than +1,5OOV mostlycorresponding to the vessels containing the shadow making agent. Nextly,the voltage applied to the opposite electrode is lowered to +l,20OV andthe latent image is developed by means of blue developer powders. Thensaid blue developer powders are attracted by the portions at a potentialhigher than +l,2OOV, that is, by the portions corresponding to thevessels and the bones. Finally, the latent image is developed by meansof red developer powders without applying a voltage to the oppositeelectrode. Then the red developer powders are attracted by all the imageportions having a positive potential.

In the X-ray electrophotograph finished through the three consecutivesteps of development by means of three kinds of developer powders asdescribed above, the image reading capability can be extremely enhanced,because the different portions are discriminated by color in such mannerthat the portions corresponding to the vessels are black, the portionscorresponding to the bones are violet and the portions corresponding tothe skins are red. If this visual image is fixed after transferred to atransfer sheet, then a preservable image can be obtained.

The present invention contemplates to cause different colors ofdeveloper powders to be selectively attracted by the selenium layer bymaking use of the difference in surface potential thereof, and themethod for development consists of the steps of providing an oppositeelectrode (S) as opposed to the selenium layer (1 properly selecting thebias voltage applied to said opposite electrode (5) in accordance withthe potential on the selenium surface, and making a given color ofdeveloper powders to be attracted by the portions of said seleniumsurface (1) corresponding to said potential. Therefore, the variousinternal organizations of the subject to be photographed can betransferred and fixed as colored selectively and separately. From suchreasons, it is enabled to transfer the various internal organizations ofthe subject as distinguished, if desired, by various different colors,so that the present invention achieves excellent functions andadvantages in that it enables easy image reading with respect to theportions of the human body for which it has been heretofore difficult toread the X-ray images.

EXAMPLE 3 FIG. 1 so that the surface potential may attain +1000 V. Afterthat, the selenium layer is irradiated with X- rays in the same manneras in Example 1. Then, the surface potential of the selenium layer isreduced to 740 V at the portions corresponding to the bones and to about400 V at other portions corresponding to the vessels, skins, etc. Thefact indicates that there exists a potential difference of about 340 Vbetween the portions for the bones and the remaining portions. Thelatent image is visualized by blowing powder cloud thereto. At thattime, the aluminum base plate-(2) is applied with a potential of 600 Vand the latent image is developed by means of negatively charged bluedeveloper powders (8) as illustrated in FIG. 8. Then, the blue developerpowders are attracted by the selenium surface portion the surfacepotential of which is higher than 600 V. Next, the potential applied tothe aluminum base plate is taken away and the whole surface of thelatent image is treated by means of negatively charged red developerpowders. Then, said red developer powders are attracted by every portionof the latent image having a positive potential. The image is thentransferred and fixed onto a transfer sheet as shown in Example 1. Thus,the portions corresponding to the bones are in violet image, while otherportions are in red image. This results in remarkable enhancement of theimage reading capability in comparison with the identification based ononly the difference in density as in the prior art.

While we have described above the principles of our invention inconnection with specific apparatus, it is to be clearly understoodthatthe description is made only by way of example and not as a limitationto the scope of our invention as set forth in the accompanying claims.

What is claimed:

1. A method of producing a multi-color X-ray electrophotographcomprising:

charging a photoconductive layer of an X-ray sensitive plate comprisinga base and the photoconductive layer, exposing the chargedphotoconductive layer to X- rays which have passed through an object tobe electrophotographed such that an electrostatic late nt image is formed on said photoconductive layer, said image having regions of reducedcharge density in accordance with the concentration of exposing X-rays,

injecting a first color developer powder onto the surface of saidphotoconductive layer, said first powder having an electrical charge ofsign opposite to that of the photoconductive layer, applying anelectrical force to said first powder, said force having a magnitudeless than the magnitude of the force which the regions of maximumpotential exert on said first powder whereby said first powder isdeposited only on those regions of said photoconductive layer whichexert a force greater than the applied force,

injecting a second differently colored developer powder onto the surfaceof said layer, said second powder having a charge of the same sign assaid first developer powder,

adjusting the magnitude of said applied force to a magnitude lower thanthe magnitude of the force exerted on said second powder by the regionon the photoconductive layer having the next highest potential such thatsaid second powder is deposited on all regions of said photoconductivelayer which exerts a greater force on said second powder than saidadjusted applied force.

2. The method according to claim 1 wherein said photo conductive layeris exposed to said X-rays only once for each multi colorelectrophotograph.

3. The method according to claim 2, wherein said method furthercomprises providing a development electrode, placing said firstdevelopment powder between said electrode and said surface of thephotoconductive layer, and the electrical force is applied to said firstpowder by impressing a potential on said electrode such that saidpotential has a sign opposite to that of said first powder and exerts onsaid first powder said electrical force which has a magnitude less thanthe magnitude of the force which the region of maximum potential exertson said first powder.

4. The method according to claim 2, wherein the step of applying theelectrical force on said first powder comprises impressing a potentialon the base such that said potential has the same sign as the sign ofsaid first powder and exerts on said first powder said electrical forcewhich has the magnitude less than the magnitude of the force which theregion of maximum potential exerts on said first powder.

5. The method according to claim 3 wherein the step of adjusting themagnitude of the applied force comprises lowering the potential on saidelectrode to a level lower than the potential on the next highestpotential region of said photo conductive layer.

6. The method according to claim 4 wherein the step of adjusting themagnitude of the applied potential comprises lowering the magnitude ofthe potential impressed on said base to a level lower than the potentialon the next highest potential region of said photo conductive layer.

7. A multi-color X-ray electrophotograph produced by the methodaccording to claim 1.

1. A METHOD OF PRODUCING A MULTI-COLOR X-RAY ELECTROPHOTOGRAPHCOMPRISING: CHARGING A PHOTOCONDUCTIVE LAYER OF AN X-RAY SENSITIVE PLATECOMPRISING A BSSE AND THE PHOTOCONDUCTIVE LAYER, EXPOSING THE CHARGEDPHOTOCONDUCTIVE LAYER TO X-RAYS WHICH HAVE PASSED THROUGH AN OBJECT TOTHE ELECTROPHOTOGRAPHED SUCH THAT AN ELECTROSTATIC LATENT IMAGE ISFORMED ON SAID PHOTOCONDUCTIVE LAYER, SAID IMAGE HAVING REGIONS OFREDUCED CHARGE DENSITY IN ACCORDANCE WITH THE CONCENTRATION OF EXPOSINGX-RAYS, INJECTING A FIRST COLOR DEVELOPER POWSER ONTO THE SURFACE OFSAID PHOTOCONDUCTIVE LAYER, SAID FIRST POWDER HAVING AN ELECTRICALCHARGE OF SIGN OPPOSITE TO THAT OF THE PHOTOCONDUCTIVE LAYER, APPLYINGAN ELECTRICAL FORCE TO SAID FIRST POWDER, SAID FORCE HAVING A MAGNITUDELESS THAN THE MAGNITUDE OF THE FORCE
 2. The method according to claim 1wherein said photo conductive layer is exposed to said X-rays only oncefor each multi color electrophotograph.
 3. The method according to claim2, wherein said method further comprises providing a developmentelectrode, placing said first development powder between said electrodeand said surface of the photoconductive layer, and the electrical forceis applied to said first powder by impressing a potential on saidelectrode such that said potential has a sign opposite to that of saidfirst powder and exerts on said first powder said electrical force whichhas a magnitude less than the magnitude of the force which the region ofmaximum potential exerts on said first powder.
 4. The method accordingto claim 2, wherein the step of applying the electrical force on saidfirst powder comprises impressing a potential on the base such that saidpotential has the same sign as the sign of said first powder and exertson said first powder said electrical force which has the magnitude lessthan the magnitude of the force which the region of maximum potentialexerts on said first powder.
 5. The method according to claim 3 whereinthe step of adjusting the magnitude of the applied force compriseslowering the potential on said electrode to a level lower than thepotential on the next highest potential region of said photo conductivelayer.
 6. The method according to claim 4 wherein the step of adjustingthe magnitude of the applied potential comprises lowering the magnitudeof the potential impressed on said base to a level lower than thepotential on the next highest potential region of said photo conductivelayer.
 7. A multi-color X-ray electrophotograph produced by the methodaccording to claim 1.